This invention relates to a method of making a compound semiconductor device and, more particularly, to a device fabrication method that includes etching material from the surface of a III/V semiconductor body by exposure to a reactive chemical medium.
In many semiconductor device fabrication sequences of practical importance, it is often necessary or at least advantageous to etch an exposed surface before depositing a layer on the surface. Illustratively, this is done before an epitaxial layer is formed on the surface of a III/V semiconductor which is to be used to fabricate electronic or optical devices. Such etching is effective to remove contaminants from the surface on which growth is to occur, thereby helping to ensure that the grown layer will be of good quality and that the resulting device will accordingly exhibit specified characteristics.
To enhance throughput and to minimize the chance of contaminating the etched (cleaned) surface, it is advantageous in a device fabrication sequence to contemplate carrying out successive etching and growth steps in situ in the same reactor. And, in fact, attempts have been reported to successively etch and grow III/V semiconductor material in situ in the chamber of a conventional growth reactor.
Chemical beam epitaxy (CBE) is a known and particularly versatile technique for growing an epitaxial layer on the surface of a single-crystal semiconductor substrate. In a CBE process, appropriate chemicals in gaseous form are introduced into a chamber and directed onto a heated semiconductor surface to produce an epitaxial layer on the surface, as is well known in the art.
Heretofore, attempts have been made to successively etch and grow III/V semiconductor material in situ in the chamber of, for example, a CBE growth reactor. But many of these attempts have been found to be deficient in the respect that known etching techniques compatible with growth conditions employed in the reactor do not usually produce etched surfaces that are sufficiently smooth. In particular, the surface roughness caused by the in situ etching process often makes the surface unacceptable for subsequent growth purposes.
Thus, it was recognized that a need existed for an improved device fabrication sequence that included an etching technique that could be carried out in a reactor under conditions compatible with a subsequent growth step performed in the same reactor. In particular, a need existed for an etching technique that could be so utilized to etch compound semiconductor materials. Specifically, it was apparent that such a technique, if available, could help to lower the cost and improve the quality of a variety of III/V semiconductor devices of practical importance.